Todd951968

My car recently started to flutter/hesitate under full throttle in the upper gears, 3-5th. I took it to the shop and they checked for vacuum leaks and haven't found any. They just called and asked if the car was chipped. Could this cause these symptoms? I have guru chips.

I've searched old archives and saw where it could be a vacuum leak but I think we've checked that. Has anyone had a chip cause this, or, have any other ideas?
Thanks

Tom M'Guinn

if just in the upper gears and just under heavy throttle, chances are high it is a weak ignition. Change the cap, rotor, plugs, and WIRES, if not new.

Todd951968

I'll check out the ignition but it seems like a boost issue

Tom M'Guinn

How so?

toddk911

+1....99% of the time for this issue.

Todd951968

The distributor, ignition harness, cap/rotor all have 23k miles on them. No record of wires being changed in 70k but I think they are magnacore if I recall correctly; car is at the shop which closed for the day. I think I need to switch garages.

The plugs have about 7k miles but looking back through the records of the PO, plugs were changed every 7-8k. Is this normal?

Tom: I assumed it was a boost/vacuum issue, based on old postings.

AlexE

I agree with the ignition components. At high boost very easy to blow out the spark on a weak system.

You should also check and see if your boost pipes and connectors are secure. They could be coming loose at full boost causing this hesitation and jerking.

theedge

Depends on the plugs (the change intervals).

What about the coil? You didnt mention that in your post.

Tom M'Guinn

Note WIRES in all caps above -- they are frequently the specifc cause. If yours have 70k, then change regardless.

Todd951968

The PO had a maintenance log in a Word document that didn't show wires being replaced; I dug up the original a receipt and it shows the wires were changed at 47k so they only have 23k miles on them. I believe they are magnacores though the part # listed is 944 609 015 90.

Hopefully , the weak link is the plugs. Though, I'll be pretty upset with my mechanic for not checking them by now.

TRWright

I had a bad ( and brand new!) rotor give me stuttering at full throttle. It was the more expensive one, too!! I changed everything in the ignition system and spent hours looking at other stuff because I knew the rotor was brand new.

(I also had a lean condition that was caused by a failed (also brand new) bosch 3bar FPR)

Moral of the story is, don't assume these parts are working just because they are fairly new.

Todd951968

tedwright: "Moral of the story is, don't assume these parts are working just because they are fairly new".

True. And the consensus here is that its ignition. So, we'll look at everything on Monday, starting with the plugs.

If anyone has any other suggestions, I welcome them. Otherwise, I'll post findings when get it sorted out hopefully next week.

35thSLP

I had this happen once and it turned out to be a very slight leak with the intake manifold gasket. easy to check for if you have some starting fluid, just spray it around each runner. If the idle goes up you have a leak.

Geneqco

I had a similar issue and it was an injector that was failing. Look for unburnt fuel - visible smoke from the exhaust when the symptom occurs and soot on the ground at idle.

Jfrahm

Check your recirculation (blow off) valve and the vacuum line to it. My Saab made a flapping noise and hesitated when I blew the control hose that opens that valve off the manifold. It was really obvious when winding up the turbo under heavy throttle and then abruptly lifting off.

It could also be ignition (depending on the noise) or a loose connection or crack in the boost piping.